Federally funded research by some of Canada's top scientists found levels of toxic hydrocarbons in six lakes between 2 1/2 and 23 times what they were before the mines were built.

A new study suggests the environmental health risks of oilsands operations in Alberta's Athabasca region have probably been underestimated.

Researchers say emissions of potentially hazardous air pollution that were used in environmental reviews done before approving some projects did not include evaporation from tailings ponds or other sources, such as dust from mining sites.

The study, by the University of Toronto's environmental chemistry research group, looked at reported levels of polycyclic aromatic hydrocarbons (PAH) — chemicals which can be released into the air, water and soil when bitumen-rich oilsands are mined and processed.

"Our study shows that emissions of PAH estimated in environmental impact assessments conducted to approve developments in the Athabasca oilsands region are likely too low," reads the study published Monday in the U.S. journal Proceedings of the National Academy of Sciences.

"The potential therefore exists that estimation of future risk to humans and wildlife because of surface mining in the Athabasca oilsands region has been underestimated."

Professor Frank Wania, one of the study's authors, said the results highlight the need for improved accounting of PAH emissions from oilsands operations, especially when more projects are being built or planned in the region.